There are 202 teams in the FIFA World Rankings, and it doesn't take a maths whizz to realise that leaves 170 teams sat at home during the tournament.
And the 32 who play in the World Cup aren't necessarily the best 32 teams playing international football.
Teams come from all over the world.
That's because the people who run football, FIFA, have made sure that lots of different regions have the chance to send teams.
Each of FIFA's six confederations - governing bodies split roughly along the lines of continents - is told how many teams they can send to the tournament.